[racket] bad syntax; literal data is not allowed, because no #%datum syntax transformer is bound

Oops.  It's not NAME that's the problem.  It's #,my-read-stx that
needs to change to (quote #,my-read-stx) instead.

Carl Eastlund

On Tue, Aug 30, 2011 at 1:41 PM, Carl Eastlund <cce at ccs.neu.edu> wrote:
> Just put an explicit "quote" form around it.  Replace NAME with (quote
> NAME) in the template.
>
> Right now there is no form to tell the expander how to expand NAME.
> So the expander looks at the lexical context to see "how do I expand
> this form".  But NAME did not come from a lexical context, so it has
> none.  You don't really want to give it some, either -- it's not a
> program, it's data.  Wrapping it with quote tells the expander what it
> needs to know via the context on the identifier "quote", and NAME can
> thus stay as data without lexical context.
>
> Carl Eastlund
>
> On Tue, Aug 30, 2011 at 6:42 AM, Neil Van Dyke <neil at neilvandyke.org> wrote:
>> I'm getting this error in some code with a macro transformer that produces
>> syntax that includes some bits of child syntax that are sourced via
>> "read-syntax".
>>
>> The below example demonstrates.
>>
>> Assuming that I really do want to use "read-syntax", how do I do this
>> properly?  (I assume that proper is not losing the "#%datum" by something
>> like "(quasisyntax/loc stx #,(syntax->datum stx))".)
>>
>>
>> #lang racket/base
>>
>> (require (for-syntax   racket/base) ;; necessary
>>        (for-template racket/base) ;; doesn't help #%datum problem
>>        (for-label    racket/base) ;; doesn't help #%datum problem
>>        )
>>
>> (define-syntax (my-macro stx)
>>  (syntax-case stx ()
>>   ((_ NAME) (let ((my-read-stx (read-syntax "my-sourcename"
>>                                             (open-input-string
>> "\"hello\""))))
>>               (quasisyntax/loc stx
>>                 (string-append "Well, " #,my-read-stx ", " NAME "!"))))))
>>
>> (my-macro "yourname")
>> ;;=exception=> compile: bad syntax; literal data is not allowed, because no
>> #%datum syntax transformer is bound in: "hello"
>>
>>
>> --
>> http://www.neilvandyke.org/